With energy declining and energy demands rising, the need for heating and cooling systems, independent or nearly independent of central electrical power sources becomes ever-increasing. Heretofore, some success has been obtained with solar heat; but the major disadvantage in solar heating systems for shelters is that demands for heat and/or cold in the shelter is heaviest when the supply of solar energy is at its natural ebb. Heat from the sun must be stored for use when the sun is not shining. Wind, as a source of energy cannot be depended upon as a source of heat during periods of calm. The wind and sun are indeed weather-sensitive energy sources. A source of energy which is not weather-sensitive may become weather-sensitive, to a certain extent, by the harnessing means employed. For example, an evaporator-condenser system which takes heat from the outside atmosphere, releasing it into the shelter, will operate more efficiently during the day when the outside atmosphere is warmer than it will during the night when the outside temperature is much lower.
Convenience controlled non-weather-sensitive heat sources are not always available on a constant basis. For example, a fireplace may be conveniently operated for only about three hours during most evenings. An oven may be operated for another two hours. An incinerator for disposal of trash or garbage may operate for yet another hour. Ultimately, all or most of these readily available "controlled" heat sources should be fully utilizable in home air conditioning systems without significant loss of heat to the outside atmosphere.
To permit continuity of air conditioning, therefore, for periods of low energy-producing weather and/or inconvenient controlled heat operation of weather-sensitive sources and/or convenience-controlled non-weather-sensitive-sources, one should look to a heat and/or cold storage facility. This facility, or unit, may be fully integrated into the auxiliary heat source, or it may be remote thereto. Most desirable is a direct heat transfer between the heat of combustion in an auxillary heating source and the liquid in the heat storage unit. Also, desirable is a direct heat transfer relationship between the heat of combustion in the auxillary unit and the living space. The former is not easily attainable with respect to shelters built before the onset of the realization that solar heat must eventually be utilized; and in such systems, heat storage units will ordinarily be remote from auxillary heat systems.
Remote or not, auxiliary or supplemental heat sub-systems should provide wherever possible, the most efficient heating means for the living space and/or the liquid heat storage medium, wherever stored; and of course it must be possible to direct the heat, on an as required basis, to either.
Prior supplemental heating systems have accomplished heating of the living space and/or heating of the heat storage medium, but not in the sense that both were direct heat transfers, in which maximum efficiency is most easily attained.
In U.S. Pat. No. 3,812,903, for example, auxillary heat is applied indirectly to the liquid in the hot or cold storage unit by means of heating the air which is blown through a rock pile, thereby circulating the air around the tank of liquid in which is contained the liquid heat storage medium. Where minimual auxillary heat is desired, as with a conventional oil or electric furnace, such an indirect heat transfer for the auxillary heat of combustion into the heat storage unit may suffice. Where part-time sub-systems, such as fireplaces or coal furnaces are employed, it may be much more desirable to create a surplus of heat for a short period of time, and to use such surplus for heating the storage medium, as well as, to a certain extent, the living space; but to insure all the while that all of such surplus heat is utilized.
In recent years, fireplaces have been improved to some extent in efficiency as an immediate source of heat. Warm air circulation systems have been provided whereby a large measure of the heat potential is circulated to the living space of a shelter. Further improvements in fireplace efficiency have not been sought because without heat storage facilities, additional heat served no useful purpose. Present day heat storage facilities do not lend themselves well to the utilization of this major home controlled heat source.